Silvaco uses cookies to improve your user experience and to provide you with content we believe will be of interest to you. Learn detailed information on Privacy Policy. By using this website, you consent to the use of our cookies.

Contact Us

TECHNICAL LIBRARY

PHILIPS Model 9

New MM9 Extraction
routine in UTMOST III

(part 1)

Introduction

In collaboration with STMicroelectronics Central
R&D at Crolles (France), a new routine has been developed in
UTMOST III to provide a complete solution for MOS Philips
Model 9 parameter extraction. This methodology[1] is based on the
local optimization method; we can determine a limited set of 18
parameters (so called miniset) to describe the electrical behavior
of each device, considering it as the reference device. This miniset
includes all the electrical parameters for an individual device[1].
Specific local optimization strategies are described in this article
to obtain good minisets. From these minisets, we can extract scaling
parameters, using simple linear regressions. We will obtain a new
complete set of parameters (so called maxisets). All temperature
dependant parameters can also be extracted.

Measures

The MM9 extraction algorithm requires measurements
from a Long and Large device, Short devices and Narrow devices (asBSIM3_MG
routine). For each device a total of six sets of I-V measurements
are requested.

Set 1: IDS versus VGS at different VBS and at
low fixed VDS.

Set 2: IDS versus VDS at different VGS and at
low fixed VBS.

Set 3: IDS versus VGS at different VBS and at
high fixed VDS.

Set 4: IDS versus VDS at different VGS and at
high fixed VBS.

Set 5: IDS versus VGS at different VDS and at
VBS=0V.

Set 6: ISUB versus VGS at different VDS and at
VBS=0V.

If these MM9 measurements are stored in a log file
and this log file is activated in UTMOST III, then the ALL_DC,
ALL_ISUB and AL_IDVGD (ID/VG-VD for several devices) can access
these measure.

Figure 1: MM9 Measurement
Setup Screen

The twenty measurement variables are used and described
hereafter.

1.

VGS_start_vg

Starting value for the
gate sweep range (ID/VG curves)

2.

VGS_stop_vg

Stop value for the gate voltage sweep
range (ID/VG curves)

3.

VDS_low_vg

Low fixed VDS bias for the ID/VG-VB
linear characteristic

4.

VDS_high_vg

High fixed VDS bias for the ID/VG-VB
saturation characteristic

5.

VDS_start_vd

Starting value for the drain voltage
sweep range (ID/VD curves)

6.

VDS_stop_vd

Stop value for the drain voltage sweep
range (ID/VD curves)

7.

VGS_strt1_vd

Calculated starting value for VGS
steps for ID/VD-VG curve (VBS=0V)

8.

VGS_strt2_vd

Calculated starting value for VGS
steps for ID/VD-VG curve (high VBS)

9.

VGS_strt_off

Offset voltage used to calculate VGS_strt1_vd
and VGS_strt2_vd

10.

VGS_stop_vd

Stop value for VGS steps (ID/VD curves)

11.

V_source

Constant source voltage

12.

VBB Maximum

VBS voltage for ID/VG- VB curves and
high VBS for ID/VD-VG curve

13.

compl_smu(A)

Current SMU's compliance

14.

points

Number of sweep data points for each
characteristics

15.

VDS_start_gd

Starting value for the VDS steps (ID/VG-VD
curve at VBS=0V)

16.

VDS_step_gd

Step value for the VDS steps (ID/VG-VD
curve at VBS=0V)

17.

VdstartIsub

Starting value for the VDS steps at
VBS=0V (ISUB/VG-VD curve)

18.

wait

Wait time in microseconds, between
measurements

19.

#_of_vgsteps

Number of VGS steps for ID/VD- VG
curves

20.

#_of_vbsteps

Number of VBS steps for ID/VG- VB
curves and for ID/VG-VD curve

Notes:

1. Variables #7 and #8 are calculated as follows:

VGS_strt1_vd = VTH(VBS=0V) + VGS_strt_off, where VTH(VBS=0V) is
the extracted threshold voltage for
ID/VGS at VDS low and VBS=0V.

VGS_strt2_vd = VTH(VBS=VBB) + VGS_strt_off, where VTH(VBS=VBB)
is the extracted threshold voltage
for ID/VGS at VDS low and BS=VBB.

2. The number of VDS step for ISUB/VGS curve
is constant equal to 3. The stop value for the VDS steps is VDS_high_vg.

3. The maximum number of points is 201 (variable
#14).

4. The maximum value for the variable #19 and
#20 is 7.

Miniset Extraction Routine

Miniset Definition

The first step of the MM9 extraction methodology
is to extract a miniset of parameters for each device, part of the
device strategy selection. For this extraction which will be based
on various local optimization strategies, we need to adjust 18 model
parameters which will be sufficient to describe the electrical behavior
of each device, considered as the reference transistor. These 18
parameters are listed hereafter: VTOR, BETSQ, THE1R, THE2R, KOR,
KR, VSBXR, MOR, GAMOOR, ZET1R, VSBTR, VPR, ALPR, GAM1R, THE3R, A1R,
A2R, and A3R. All the scaling parameters (SLxx, SWxx, and STxx)
must be set to 0.

Figure 2: The six
measurement characterization for MM9 Routine.

Clipping Note

In order to obtain accurate minisets, the MOS level
9 model has been slightly modified. The first modification concerns
the parameter clipping. We have introduced a new parameter NOCLIP.
If set to 1, clipping on THE3R and GAM1R is removed. Negative value
for THE3R can be found for long and wide devices. This NOCLIP has
been also introduced for GAM1R, to allow negative values during
the optimization; but this almost never appears. The user may take
care using NOCLIP=1. If THE3R is too negative, solver may not converge.

The second modification concerns the de-activation
of the weak and moderate inversion modeling by using ZET1R value,
weak inversion factor, as a switch. When ZET1R>5, there is no
more subthreshold current. But, the linear region modeling remains
the same. A better optimization of the first-order parameters can
be performed.

These two modifications are useful to get an accurate
miniset using the local optimization strategies.

User Initial Model Parameter Values

Before launching the extraction procedure, it is
important to define the initial value for the model parameters to
be optimized. KR and VSBXR model parameters describe the high back
bias body effect. These two parameters may not be extracted if only
one body effect appears in our technology. For that matter, we can
use the ID/VG-VB or LGAMMA routine. Using the "Fit" option,
and displaying the:

If we do not obtain a straight line, we have to
use KR and VSBXR to describe the two body effects. Tables 1, 2 and
3 summarize the initial values of the miniset parameter.

Parameters

1 Body
Effect

2 Body
Effect

KOR

0.6

0.6

KR

Not Important

0.3

VSBXR

100

1

ETAMR; not optimized

1

2

ETAGAMR; not optimized

1

2

Table 1. Initial
values for miniset #1.

In Table 2, these values can be adapted if one
strategy does not give good results. This may happen if initial
values are really too far from values to obtain. Minimum and maximum
values are also important for local optimization strategies. The
table below gives you an example of possible minimum and maximum
values.

Parameters

Initial
Value

Parameters

Initial
Value

Parameters

Initial Value

VTOR

0.7

VPR

1.5

PHIBR

0.65

BETSQ

1.E-4

ALPR

0.01

LAP

0

THE1R

0.1

THE3R

0.01

WOT

0

THE2R

0.1

VSBTR

100

LER

Mask Length

MOR

0.5

A1R

3

WER

Mask Width

GAMOOR

5.E-4

A2R

20

LVAR

0

ZET1R

2

A3R

1

WVAR

0

GAM1R

0.01

ETADSR

0.6

TR

Temperature

Table 2. Table 1.
Initial values for miniset #2.

Parameters

Minimum

Maximum

Parameters

Minimum

Maximum

VTOR

-2

2

ZET1R

0

5

BETSQ

1.E-6

1.E-3

VSBTR

0

100

THE1R

1.E-3

2

VPR

0.05

100

THE2R

1.E-8

0.5

QLPR

1.E-7

0.1

KOR

0.01

1.5

GAM1R

1.E-5

0.5

KR

1

0

THE3R

-0.05

1

VSBXR

0

100

A1R

0

30

MOR

0

2

A2R

10

100

GAMOOR

1.E-9

0.1

A3R

0.1

10

Table 3. Table 1.
Initial values for miniset #3.

All the scaling parameters (whose names begin with
SL, SW or ST) must be set to 0. TR will be automatically set to
the measurement temperature during the miniset optimizations.

All these initial values must be copied in the
User column of the Parameter screen.

Optimizer Setup

The recommended optimizer setup is illustrated
in the figure below.

Figure 3. Optimizer
Setup recommended.

Local Optimization Strategies

Nine local optimization strategies are proposed.
The name given to the strategies is not important, and can be changed
without any problem. The strategy number is important. Utmost III
will choose by his own which strategy to apply, depending on the
type of transistor we are working on. The "Geometry Selected
Screen" we can define in the "Target Selection Screen"
is not important, as we apply the local optimization only on the
device displayed on the "Graphics Screen". MM9 Routine
will recognize the type of device we have selected in the Strategy
Screen, and then order them to execute the minisets optimization.
First we work on the Long&Large device, then on the short devices,
and finally on the narrow devices.

The optimized parameters are: VTOR, BETSQ, THE1R,
KOR, THE2R, KR, VSBXR. During the optimization, ZET1R is automatically
set to 100, which will disable the weak and moderate current modeling.

Strategy #3: Weak and moderate inversions:
subth_#vds_mm9_min.

Figure 6. subth_#vds_mm9_min
Local Optimization Definition.

The optimized parameters are: MOR, GAMOOR, ZET1R.
Before executing this optimization, ZET1R is automatically set to
a value lower than 5 to enable weak and moderate current modeling.
As MOR and ZET1R are strongly correlated, you may adjust this strategy
if the result obtained is not good enough.

The optimized parameters are: VPR, ALPR, and eventually
GAMOOR. For the long&large device, VPR is optimized. LER is
automatically set to the length value of the transistor displayed.
Like this VPR is identical to Vp. The default GAM1R is 0. GAMOOR
has been normally already extracted from the subthreshold region,
but may need to be optimized again in that region if more accuracy
is needed for low VGS.

The optimized parameters are: ALPR, GAM1R and eventually
GAMOOR. VPR is calculated using the following formula: As for the
long&large device, GAMOOR may need a new optimization especially
for low VGS. LER is automatically set to the length of the device
displayed.

The optimized parameters are: ALPR, GAM1R, and
eventually VPR. VPR and LER are calculated as for the short devices.
Although there is no scaling rule for Vp, VPR may need new optimization
for narrow devices.

We work now on ID/VD-VG at VBS=0V and for different
VGS.

Strategy #7: Saturation current: IDvsVD_mm9_min.

Figure 10. IdvsVD_mm9_min
Local Optimization Definition.

The optimized parameter is: THE3R. Take care that
minimum value for THE3R may not be lower than ­0.005.